Electromechanical oscillating device



Jan. 20, 1970 K. s. .RODAWAY ELECTROMECHANICAL OSCILLATING DEVICE Filed Oct. 25. 1 967 INVENTOR. KEITH S. RODAWAY fffiod'f/ mbuw ATTORNEYS -FIG.4

United States Patent 3 491 279 ELECTROMECHANIGALbSClLLATING DEVICE Keith S. Rodaway, Palos Verdes Peninsula, Calif. (511 N.

ABSTRACT OF THE DISCLOSURE An electromechanical oscillating device is provided for rapidly oscillating utilitarian implements such as toothbrushes, knife blades, or the like. The device incorporates within a hollow casing a mass guided within the casing for back and forth movement together with a spring tending to hold the mass in a given position. Electromagnetic coils are disposed in flux Coupling relationship with a portion of the mass defining an armature. The natural resonant frequency of the mass and spring combination is made an integral multiple of the exciting alternating current for the electromagnetic coils. Suitable bumpers may be provided to'limit the amplitude of oscillation.

This invention relates to electromechanical devices and more particularly to an improved electromechanical oscillator for oscillating any desired utilitarian structure such as a knife blade.

Oscillating devices for household use such as electric toothbrushes, electric knives, and similar consumer products usually incorporate a simple electric motor operable from the conventional A.C. 60-cycle power available in most homes. The rotary motion of the motor in turn is converted to a reciprocating motion to effect the desired oscillations. While these devices are effective, they generally involve a large number of moving parts which not only increases the bulk and expense of the device but also increases maintenance problems.

With the foregoing in mind, it is a primary object of the present invention to provide a greatly improved electromechanical oscillating device preferably for domestic use wherein the foregoing problems are, to a considerable extent, overcome.

More particularly, it is an object to provide an electromechanical oscillating devices which incorporates a minimum number of moving parts such that the bulk of the device is substantially reduced as well as expenses involved in the manufacture thereof. In addition, with fewer moving parts, maintenance problems are almost nil.

Briefly, these and other objects and advantages of this invention are attained by avoiding the conventional step of converting rotary motion from an electric motor into the desired oscillating or reciprocating motion and rather effecting oscillating motion directly from the alternating current source available. Towards this end, advantage is taken of the fact that very little power is required to sustain a natural mechanical resonance of a given mass. Thus, in accord with the invention, the member to be oscillated is mounted for direct oscillatory or reciprocating movement in a suitable guide means which may constitute part of a casing. A spring in turn is secured between the casing and member and the mass of the member and spring constant are so designed as to provide a desired natural mechanical resonant frequency. Suitable electromagnetic field generating means, preferably in the form of E cores and coils, are positioned in the casing in flux coupling relationship with a portion of the mass defining a laminated armature. The arrangement is such that exciting the coils with conventionally available 60-cyc1e household current will effect the de- Patented Jan. 20, 1970 sired oscillation of the mass. By adjusting the given natural mechanical resonant frequency of oscillation to be equal to the frequency of the available power such as 60 cycles or to an integral multiple thereof, such as one of the harmonics of the power frequency, oscillations may be sustained with very little electrical power being expended. Moreover, as a consequence of this arrangement, there is basically present only one moving part in the form of the oscillating mass itself and thus a compact configuration may be provided and there is substantially no maintenance with respect to the device itself.

A better understanding of the invention and further features and advantages thereof will be had by now referring to one embodiment as illustrated in the accompanying drawings, in which:

FIGURE 1 is a perspective view of an electric knife incoporating the electromechanical oscillating device of this invention;

FIGURE 2 is a fragmentary cross section taken in the direction of the arrows 2-2 of FIGURE 1;

FIGURE 3 is another fragmentary cross section taken in the direction of the arrows 33 of FIGURE 1;

FIGURE 4 is a diagram of the electrical portion of the device; and,

FIGURE 5 illustrates a series of wave forms useful in explaining the operation of the invention.

For purposes of describing a preferred embodiment of the invention, the device is shown as taking the form of an electric knife. It should be understood, however, that the oscillating structure may be used to oscillate implements other than knife blades.

Thus, referring to FIGURE 1 there is illustrated a handle 10 for an electric knife which may constitute a suitable casing for incorporating the oscillating mechanism. The knife blade is illustrated at 11 and is received within an end slot 12 in the casing 10. An electric cord 13 extends from the rear of the casing for connection to conventional household 60-cycle alternating current. An on-olf switch S is shown on the upper forward portion of the casing for easy operation by a user.

Referring to FIGURE 2, the knife blade 11 is shown as secured to an extending portion 14 capable of guided back and forth oscillatory movement over a small amplitude within the casing 10. Towards this end, the slot 12 extends Within the casing wherein there are by the casing walls defined a guide means 12a and 12b for upper and lower spaced portions 14a and 14b for the member 14. The member 14 together with the knife blade 11 constitute an overall mass which is reciprocal along the guide means defined by the end slot extending into the casing. When a knife blade is to be oscillated, it is convenient to provide a simple means for detaching the blade for cleaning purposes and towards this end, the member 14 may include end openings or slots such as indicated at 15 and 16 for receiving extending fingers 17 and 18 forming an integral portion of the base of the blade 11. The particular manner of detachably securing the blade 11 to the member 14 may be accomplished by other means the important fact being that the overall mass of the member 14 and blade 11 considered together be known.

Between the upper and lower spaced portions 14a and 14b of the mass there is provided a transversely extending portion as illustrated in cross section in FIGURE 2 at 14. This portion defines an armature and preferably is laminated. The overall structure appears H shaped in cross section. In the spaces between the portions 14a and 14b on opposite sides of the transverse armature portion 14 are disposed coil cores 19 and 20 preferably of the E type incorporating suitable coils as indicated. The cores and coils are secured in a stationary position relative to the guide means and casing as by suitable bolts 21 and 22. Electrical leads from the coils are indicated at 23 and pass through the switch S and to the cord 13 so that the coils may be excited from conventional 60-cycle household current.

Referring to the forward portion of the mass 14, there is provided an additional transverse portion 14" between the upper and lower portions 14a and 14b, this latter portion being axially spaced ahead of the E core and coils and armature portion 14. In the spaces between the portions on either side of the additional transverse portion 14" there are provided spring means in the form of stationary spring end supports 24 and 25 carrying first ends of suitable springs 26 and 27 shown engaging opposite sides of the transverse portion 14". These springs thus bias the mass 14 to a given center position within the casing 10, this position being midway between the coil cores 19 and 20 in the absence of any current supplied thereto.

In addition to the springs 26 and 27, there may be provided suitable bumper means 28 and 29. As shown, these bumper means are also disposed on opposite sides of the transverse portion 14" and are so spaced as to be engaged by the transverse portion 14" at maximum amplitudes of oscillation of the mass 14. These bumpers thu-s limit the maximum amplitude of oscillation to that indicated by the double headed arrow 30 in FIGURE 2, shown above the armature 14'.

In the hollow interior of the casing to the right as illustrated in FIGURE 2 there are provided diodes D1 and D2 constituting part of the electrical circuit. The function of these diodes will become clearer as the description proceeds.

In the top view of FIGURE 3, the arrangement of the upper portion 14a of the mass 14 relative to the casing will be evident. It will be noted in this respect that the -bolts21 and 22 for securing the E cores 19 and 20 extend into the far wall of the casing as shown to hold these cores in a stationary position relative to the casing.

Referring now to FIGURE 4, the electrical connections to the various coils are indicated schematically wherein it will be noted that a plug 31 on the end of the cord 13 when inserted in a conventional outlet socket will pass energy through the leads 13, switch S when the same is closed, to leads 32 and 33. These latter connections connect across the coils on cores 19 and 20 and the diodes D1 and D2 respectively connected in series with the coils as shown.

With the foregoing arrangement, the diodes D1 and D2 will rectify the alternating current supplied to the coils in such a manner that the coil for the core 19 will receive positive half cycles and the coil for the core 20 will receive negative half cycles.

The foregoing will become clearer by referring to FIG- URE wherein there is illustrated at 34 the conventional A.C. 60-cycle sine wave received on the leads 13.

Wave form B indicates the rectified current passed to the coil for the core 19 and it will be noted that this current constitutes positive half cycles 35. Wave form C represents the portion of the current passed to the coil for the core and is represented by negative half cycles 36.

With the foregoing description of the device in mind, its operation will now be described. The plug 31 of FIG- URE 4 is initially inserted in a suitable 60-cycle outlet. When the switch S is closed, the coils on the cores 19 and 20 will be alternately excited with positive and negative pulses as described. These coils are in flux coupling relationship with the laminated armature portions 14 of FIGURE 2 and thus the armature 14' will be alternately attracted to the respective E cores.

The overall mass of the member 14 and blade 11 and the spring constant for the springs 26 and 27 are so adjusted that the given natural mechanical resonant frequency of the mass and spring combination has a given relationship to the 60-cycle line frequency such that oscillations at the natural resonant frequency will be sustained by the magnetic field. This relationship preferably conslitutes an integral multiple of the line frequency and if this multiple is unity, the mass 14 will oscillate sixty times a second. The amplitude of oscillation will be limited by the bumpers described at 28 and 29 in FIGURE 2.

Since the natural mechanical resonant frequency of the member 14 and blade 11 bears the described relationship to the 60-cycle line frequency or frequency of the pulsating magnetic fields generated by the respective cores, very little energy is required to maintain the oscillations of the mass. As a result, a highly eificient oscillating device is provided.

If desired, the mass and spring constant of the structure may be adjusted so that the multiple of the exciting frequency is two or three in which event extremely rapid oscillations of the blade will take place. The amplitude of oscillation as indicated by the double headed arrow v30 is preferably kept small as physically indicated. The rapid oscillations result in an extremely effective cutting operation.

It will be further evident from the foregoing description, that there is essentially provided only a single moving element in the form of the mass 14. The conversion of the electrical energy into mechanical oscillatory movement is thus extremely efficient and the entire physical arangement of the oscillating mass with respect to the disposition of the cores and coils results in a very compact and neat configuration.

It will be evident accordingly, that the present invention has provided an improved electromechanical oscillating device wherein all of the objects set forth are fully realized.

What is claimed is:

1. An electromechanical oscillating device comprising, in combination: a hollow casing having an end slot extending there into and inner wall portions defining a guide means; a mass mounted for oscillatory movement in said guide means, at least a portion of said mass defining an armature; spring means having a first end in a stationary position relative to said guide means and a second end engaging said mass to bias said mass to a central position in said guide means so that if said mass is moved from said central position and released, it will oscillate back and forth at a natural mechanical resonant frequency determined by said mass and the spring constant of said spring means; a magnetic field generating means comprising E cores wound with coils and positioned in said casing on opposite sides of said armature along the axis of said guide means; means connected to said coils to excite the same with alternating current; and rectifier means in series with each coil such that one of said coils is excited with positive half cycles of said current and the other is excited with negative half cycles whereby said armature is alternately attracted to said cores, said natural mechanical resonant frequency of said mass and spring means constituting an integral multiple of the frequency of said magnetic field generating means said mass defining elongated spaced portions in sliding engagement with opposite interior wall portions of said casing, said portion defining said armature extending transversely between said spaced portions to define an H shape in cross section, said cores and coils being disposed between said spaced portions whereby a compact configuration is provided.

2. A device according to claim 1, including bumper means on opposite sides of a portion of said mass in positions to limit the maximum amplitude of oscillation of said mass.

3. A device according to claim 1, in which said mass includes an additional transverse portion extending between said spaced portions axially spaced from said cores; and spring biased bumper means secured to said casing between said spaced portions on opposite sides of said additional transverse portion and at given spaced intervals therefrom to define the maximum amplitude of oscillation of said mass in said casing.

4. A device according to claim 1, in which said mass includes a knife blade extending from said end slot to provide an oscillating cutting means.

2,938,269 5/1960 Wissen 30272 7/1965 Marini 318-125 XR 10 6 2,145,711 1/1939 Critchfield et a1. 31029 2,568,757 9/1951 Mesh 310-29 XR 3,293,515 12/1966 Klemm 310-29 XR MILTON O. HIRSHFIELD, Primary Examiner B. A. REYNOLDS, Assistant Examiner US. Cl. X.R. 

